hiya
first look in the registry keys view
if you see any entries for .vsd or .vdx then they are probably wrong, but read them anyway. they may contain things like arguments to VisioViewer.EXE (or whatever it is)
Find the
Component VisioViewer.EXE and go to advanced->extensions
make sure that you have .vsd and .vdx
have you had a look at the new book "Administrator's Introduction to Application Repackaging and Software Deployment using Windows Installer"
you can get it from
www.installsite.bizlooeee